2024-05-17_REVISION - M1977493 (4)

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G-2.3 Current Process Water Area As shown on Figure G-03,the current process water area is approximately 5839 acres(9.12 sq-mi). Runoff from this area reports to the Sludge Densification Plant(SDP) and the Property Discharge Water Treatment Plant(PDWTP)for treatment and release from site or is consumed on site. Historic system flows provide an estimate of current process water flows. The average annual discharge from the PDWTP over the last 9 years (2013 to 2022) has been about 9,340 acre-feet(approximately 5,800 gpm average annual rate). The average annual consumptive use at the site due to mining operations over the last 9 years has been 2,310 acre-feet (approximately 1,430 gpm average annual rate). G-2.4 TSF Development Tailings are deposited onto the TSFs at Climax using the upstream deposition method through a header and spigot tailing distribution system,similar to long-standing prior practices at the site. As the tailing slurry flows toward the water pool,the coarser tailing sands settle out first and become deposited on the beach between the dam crest and the water pool. The build-up of tailing sands on the beach effectively raises the height of the dam crest thereby creating additional water storage capacity. The finer tailing materials ("slimes") are transported to the water pool, where they settle to the bottom. During the summer months,tailing is deposited onto the beach through multiple spigots from a crest header line to promote dam crest raises. The spigot deposition period typically lasts about five to six months, depending primarily on weather conditions. Spigot deposition raises the dam crest level creating storage space for leadoff tailings and process water. During the winter, shallow tailing slurry deposited from spigots would tend to freeze and could create ice lenses and permafrost near the dam crest. These frozen zones could have stability implications on the TSF and the build-up of ice at the ends of the spigot pipes could restrict slurry flow toward the water pool. To mitigate these risks,tailing is deposited through larger-diameter and longer leadoffs during the winter months. These leadoffs produce a tailing stream that prevents saturation of the beach area near the dam crest. Tenmile TSF, which is formed by 3 Dam, is an existing facility that was first developed in the 1950's. The original AM-06 mine plan called for the deposition of approximately 26 million tons of additional tailing in the facility; primarily during the first few years of mineral extraction and production. The additional deposition is expected to raise the dam crest elevation by about 25 feet. As of the end of 2022, approximately 22 million tons of tailings have been deposited in Tenmile TSF. As shown on Figure G-01,tailing slurry is delivered to Tenmile TSF through a tailing delivery line (TDL) that generally follows the route of the ETDL. The ETDL continues to be used to route impacted water sources to the SDP. Mayflower TSF, which is formed by 5 Dam, is an existing facility that was initially developed in the 1970's. The original AM-06 mine plan called for the deposition of approximately 180 million tons of additional tailing in Mayflower TSF. The additional deposition is expected to raise the dam crest from its current elevation at about 10,610 feet to about 10,820,which constitutes a 210-foot raise. As of the end of 2022, approximately 40 million tons of tailings have been deposited in Mayflower TSF. As shown on Figure G-01,tailing slurry is delivered to Mayflower TSF through tailing delivery lines (Mayflower TDL)that generally follows the route of the original tailing delivery line that extends from 3 Dam to 5 Dam. From the mill to 3 Dam,the TDL installed as part of the mine restart project will continue to be used. The existing ETDL continues to route impacted water sources to the SDP. Although Mayflower TSF is the primary storage facility going forward,Tenmile TSF remains operational as a backup if needed for tailings deposition. G-2.5 Mill Water Reclaim Systems When tailing is being deposited on Tenmile TSF, the tailing slurry from the mill and SDP effluent will contribute process water to Tenmile TSF. The water level on Tenmile TSF can be controlled through operation of the Tenmile Decant,which conveys all flows from Tenmile TSF into the Tenmile Tunnel. Inside the tunnel, bulkhead valves can be configured to direct water south to Robinson Lake or north to Mayflower TSF. From Robinson Lake, process water is delivered to the storage tank at the mill using the Robinson Lake Pump Station and Reclaim Pipeline. This reclaim system is sized to meet the full mill water demand with a Exhibit G G-4 May 2024